Some telecommunications network routing elements, such as signal transfer points and SS7/IP gateways, have distributed internal processing architectures. In such architectures, different processing modules or cards perform different telecommunications functions. For example, some processing modules or cards may interface with external signaling links. Other processing modules or cards may perform maintenance and control functions. Still other processing modules or cards may perform database-related services for received signaling messages.
In order for a routing node with a distributed internal processing architecture to function properly, it is necessary to provide a mechanism for inter-processor communication. One conventional method for inter-processor communication is to use a ring topology. FIG. 1 is a block diagram of a conventional signaling message routing node where processing modules or cards are connected via a ring topology. Referring to FIG. 1, signaling message routing node 100 includes a first shelf 102 and a second shelf 104. Shelves 102 and 104 each include a plurality of processing modules connected to each other via counter-rotating, dual-ring buses 106. In the illustrated example, shelves 102 and 104 include link interface modules (LIMs) 108 for interfacing with external SS7 or IP signaling links, database services modules (DSMs) 110 for providing database-related services, such as LNP and global title translation, an operations, administration, and maintenance (OA&M) module 112 for performing maintenance functions, and a high speed multiplexer (HMUX) 114 for providing communication between shelves via high speed, counter-rotating, dual-ring buses 106. For interprocessor communication, modules 108-112 each implement a protocol stack that includes an interprocessor message transport (IMT) layer 118. HMUX cards 114 may also implement an IMT layer 118. In addition to IMT layers 118, modules 108-112 may also implement an SS7 layer 120.
IMT layers 118 provide link level communications between processor cards via a ring-topology-based link level communications protocol, referred to as the IMT protocol. The IMT protocol defines packet formats, determines card presence and availability, and establishes connections between cards. The IMT protocol is also used to carry SS7 signaling messages between cards.
One important function of the IMT protocol is to distribute special-purpose messages to all shelves in the routing node and return the messages to the sender. Examples of special-purpose messages that must be distributed and returned to the sender include flow control messages and test signaling units (TSUs). One type of flow control message used in signal transfer points is referred to as a ticket voucher request. A ticket voucher request may be originated by a link interface module in one shelf when the link interface module receives a message signaling unit (MSU) requiring SCCP service. The ticket voucher request is distributed to all shelves. A shelf having a database services module with available processing capacity will grant the request and modify the ticket voucher request to indicate that the request has been granted. The ticket voucher request message is returned to the originating link interface module after being distributed among all shelves.
In a ring topology, such as that illustrated in FIG. 1, distributing messages among all shelves and returning the messages to the originating card is easy because the cards and shelves are arranged in a ring topology and the IMT protocol provides a mechanism for such distribution and return. In this mechanism, when a card originates a message with the IMT source address being equal to the IMT destination address, that message is automatically distributed among all shelves in the ring topology and returned to the originator. The same mechanism can be used to distribute TSUs and return the TSUs to the originator.
In light of the availability of low cost hardware for high-speed link level communications, such as gigabit-Ethernet hardware, it is desirable to migrate from ring-topology-based link level topologies and communications protocols to high-speed link level communications protocols. One problem with migrating to a new link level communications protocol is that existing link level communications functions should be preserved. For example, the function described above where a message is distributed among all cards in a ring and returned to the originator does not map directly to gigabit Ethernet because gigabit Ethernet is based on a star topology, and gigabit-Ethernet does not allow source addressed frames. Accordingly, there exist a need for improved methods and systems for distributing packets of a ring-topology-based link level communications protocol using packets or frames of a star-topology-based link level communications protocol.